I don't really know... I never really pay much attention to Lipo related stuff, but it seems to be a regularly discussed topic on the RC Groups forum (puffy lipos). This might be one you could to start with:

Dogman, was this pack puffy straight out of the box from HK or after you ran it hard on your mountain bike?

I am trying to determine what the life and failure rate is for the regular Turnigy batteries. Is it as high as 10% of the packs fail or puff even when not overdriven? I really have no idea from all of the posts I have read.

I am interested in the Nanotech batteries if they are longer life and less prone to this type of puff. I'll gladly pay up to 2x the price of the normal Turnigy if I could get a battery that I am 99.9% sure will work fine for 2 to 4 years (and arrives to me with no bad cells).

Puffed as hell, straight out of the box. Now I've joined the HK club. Maybe I'll run it a few cycles, if discharging it should be ok. I can charge it outside.

If nothing else, I have some cells for repairing a pack.

On another subject, some wires and plugs and a small camera ordered a week earlier have been either going back and forth to china, or went to switserland, I'm not sure which. While the batteries zipped right to me.

So say I wanted to minimize the "puff" chance by going with the nanotech batteries (at least it claims in the description the puff is 5% vs 15% for normal ones) and I also wanted to minimize the downtime to the pack if it needs repair.

I am really torn if I want to go with 2s packs and do a lot of wiring but have easier time repairing (if nanotech turns out to have similar failures) or if I should go with 3s, 4s or 6s packs with easier wiring...

The Puff reduction from Nanotech cells is for when they are used at full C rate or in other words discharged at extremes.

Dogman - what was the voltage on the puffy cell?

My best guess (slightly educated now) would be on shipping it's the outter cells which will arrive puffed... I have to chalk this up to FLAT IMPACT, not piercing but just being thrown around with minimal padding between them... I base this on several packs which I've caused the same problem with having them (dont laugh please) velcroed strapped to my rear rack for testing...

The only way to get them puffed under normal use (10C?) is to over discharge them past 3v per cell... even then if you catch it soon enough and trickle charge the over discharged cells to nominal before resuming normal charge rates - the puff is avoided.

I've got a pack here which is SOOOO bloated it's as wide as a 9C (1x6S and 1x3S) together (it was a 6S to begin with)... that one was from discharge testing trying to blow it up but it failed to ignite (man did it say "Super Size Me" though).

If the voltage wasn't odd - I would lance it gently... remove as much of the gas (don't clamp it tight) and as Luke pointed out... a drop of glue or epoxy should do the trick.

liveforphysics wrote:
That seems to be working well for KiM, and I don't see it adding much risk of it going off, but treat it like it could when you charge.

Indeed it has...Dogman i wish my puffed cells were only that puffed mine look like bloated
roadkill...haha As Luke mentioned too my de-puffed and resealed lipos packs are going fine
all balance within 0.01v of each other hot off the charger i been pulling as much as 280amp from them too
so they ain't being babied...
...I forget how many cells i have 'de-puffed' now...two and a a half 6s packs worth or there abouts though.
Make sure if you try this though you use a non metallic object to pierce the cell, apply minimal pressure AFTER the
cell is lanced, you don't want so much pressure that liquid comes out of the pack IMO.
... i cut a slice a few mm long right on the seem, released the gass then applied a
smear of hot glue and folded the seam back down over the slice/glue and re taped the pack
with 4 wraps of Kevlar tape.

KiM

EDIT: I of course mention all this with word of caution, if your house burns down due to lipo fire don't come running to
me crying I been charging mine inside on wood table or in my bikes fiberglass battery housing
from day one and haven't changed this routine...

Ok this is going to sound a bit crazy, but has anyone tried putting a puffed pack in a bell jar and pulling a vacuum on it? If it is hydrogen inside the packs puffing them up, the very small atoms might diffuse through the thin foil over a period of several hours with a high vaccum. Or it might do nothing...

Dang, I have three 2 stage vacuum pumps, one that can pump down below 10 milliTorr (a Welch DuoSeal) but no Turnigy packs yet. Actually I am hoping I never have this puffy problem to deal with

Cocktail sticks or tooth picks would do nicely Knoxie...I used a box cutter blade
on all mine one though i sparked when i cut it next there was a foot high
burst of sparks and thick white smoke that filled the garage, all from one
lil cell was quite amazed what came out of it, i been meaning to try and replicate this
and catch it on camera LoL

Forgot to mention that the cell had normal voltage. It charged up normal last night too. Something popped at some point, and let the toxic gas out, but I can't tell where it got out. The seam on top I guess.

Leaving it unsealed will let air in that kills it? We'll see now I guess. I just taped it back up to compress it.

dogman wrote:Forgot to mention that the cell had normal voltage. It charged up normal last night too. Something popped at some point, and let the toxic gas out, but I can't tell where it got out. The seam on top I guess.

Leaving it unsealed will let air in that kills it? We'll see now I guess. I just taped it back up to compress it.

The organic solvent inside the pouch is critical to cell function, an will evaporate out if it's not sealed. Also, at least in theory, if oxygen and water vapor get inside the pouch, it should do bad things, yet in practice the most reaction I got was just mild warming.

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liveforphysics wrote:The organic solvent inside the pouch is critical to cell function, an will evaporate out if it's not sealed. Also, at least in theory, if oxygen and water vapor get inside the pouch, it should do bad things, yet in practice the most reaction I got was just mild warming.

Based on my understanding from the battery geeks I've spoken with, the most likely result letting in a little bit of oxygen / water vapor is that the cell capacity will degrade more quickly with cycling than its untainted neighbors.

Long as it lasts till the next time I order from HK that works for me. It doesn't look like trying to seal the top of the pouch will be very easy with it soldered on. May as well get a half dozen cycles out of it and then retire it till I need repair cells or have a use for a 3s pack.

Any idea on how to minimize the chance of this in the future dogman? How was the packing? Do you think one huge order is better, or several small orders?

I want to create a big (for me) 15s4p lipo which I would charge to 4.1V but I don't have a good feeling for how much *overage* I should figure in when ordering cells if there is going to be a significant chance of a bad pack or two. Do you usually order around 10% more than what you need?

I've been running 20ah of puffed 5s4p lipo with absolutely zero issues on your old brushed WE hub Dogman. The puffed cells stay balanced better than the 6s4p 20ah pack they are in series with. Approaching full discharge, the puffed cells stay balanced within a couple thousandths of a volts, the 6S stay balanced within .2 volt. So about 10x better balanced!

Discharge rate is limited to 26A and they are charged at 5A. I run 'em puffed, but I ain't that stupid. These cells were puffed by miswiring the pack on the first trip out. I accidentally wired the packs in parallel rather than series and rode for under 5 minutes to the store. I went to unplug the pack and noticed one of them was HOT! I realized what was going on within a few seconds -DOH! and yanked the plugs. The 6S pack had been trying to balance with the 5S pack. The 5S pack cells made it to 4.5 volts, but puffed. A new wiring harness was made PDQ!

If the puffing is keeping you from using them due to size, then I'd trying deflating them, if not, keep on truckin', but gently.

My original pack (now mostly retired) survived about 200 cycles of use after puffing so badly that I really thought it would explode in use - to the point where I custom lined a topeak trunk with Lipo bags (big nomex / kevlar type cut into panels and epoxied into place)... but in the end, even my worst puffer which again is about 9S wide for a 6s runs fine at 20-40A (I'm not fool enough to push my luck past 8C).

Popping a tiny hole in the surface very quickly knead the air out (you can put the hole right in the wide side... the puffiest part, then just use some hitemp muffler or even better clear packaging tape (some of it's good to 120C) just to seal over the hole and maintain the seal when they heat to 100-110 degrees in operation.

I've got 1/2 of my first 15S pack done up this way after hyena's suggestion in another thread, figured worst case would be a dead pack... that one is still in service (it was about the same puff level as your pack).

You could have just shipped it back to em slow boat style for warranty replacement, not that I ever have either

So far I had 2 messed up packs when I first started (on arrival) but... to date only one other pack had issues, a 2S which had 1 cell at about 2.4v on arrival but no puff... charged to 3.3v @ 100ma then hit it with 1C... pack stays balanced and works fine!

I'm pretty sure the 2,3 and 4S just came back into stock... the others should be available now.

Finally someone asked about ordering and adding overage to the orders... My rule of thumb is no more than 4 x 6S packs (usually 3) and I always throw in some small delicate bits (connectors, a 1.00 foamie airplane part, etc) then EMS to USA... If I'm ordering a motor or somthing similar which would arrive wrapped in padded pop wrap, I never put those in with the shipments of batteries... Wire is heavy and kinda defeats the purpose but shrink wrap is great for adding extra padding to a shipment of lipo - so are those 2.00 sheets of foam they sell, 1 or 2 of those in an order and you would be surprised how well it's all packed into the box

Well Dogman, I am going to try the same packs as you. I just ordered four of the 4s 20C turnigy and two of the 6s 20C turnigy, giving me 14s2p for $220. I didn't really want to ship quite that much in one package but I implemented mwkeefer's strategy of adding some connectors and airplane foam to the order...hopefully it forces them to use a bigger box.

I feel a bit like I am pulling a lever on a slot machine...it is actually sort of exciting...do I get a 500 watt battery for $220 or will I be unlucky